1. Technical Field
The present invention relates to a production unit for a liquid crystal display panel and a manufacturing method for a liquid crystal display panel and in particular, relates to a substrate cleaning apparatus for cleaning a substrate included in a liquid crystal display panel and a substrate cleaning method using the same.
2. Background Art
As a display device of audio and visual (AV) equipment or an office automation (OA) equipment, a liquid crystal display device is used widely, since the device is thin, light in weight and low power consuming. This liquid crystal display (LCD) device includes an LCD panel including a first substrate, a second substrate and a liquid crystal (LC) layer disposed between the two substrates. Switching elements such as thin film transistors (TFTs) are formed in a matrix shape on the first substrate (hereinafter, referred to as a TFT substrate). A color filter (CF) and a black matrix (BM) or the like are formed on the second substrate (hereinafter, referred to as a CF substrate).
The above-mentioned LCD panel is formed in following procedures, for example,
(1) cleaning a TFT substrate and a CF substrate, and drying them;
(2) printing/curing alignment films on surfaces of the TFT substrate and the CF substrate facing each other;
(3) rubbing the alignment film;
(4) cleaning the substrates, and drying in order to remove fibers of rubbing cloth or shavings of the alignment film;
(5) spraying one of the TFT substrate and the CF substrate with spacers, and fixing the spacers;
(6) applying a sealing material and a transfer material on the other substrate; and
(7) dropping a liquid crystal material and sealing the substrates.
In the above-mentioned LCD panel, an alignment direction of an LC molecule is controlled by an electric field which electrodes provided on either or both of the substrates generate. The above-mentioned LCD panel displays images based on the control. When foreign objects remain on the TFT substrate or the CF substrate, a gap between the substrates is formed nonuniformly. Due to the gap being nonuniform, displaying quality deteriorates. Accordingly, cleaning of a substrate is important particularly for a large LCD panel. Thus, large substrate cleaning has been performed using various kinds of methods.
In a substrate cleaning apparatus, a substrate is conveyed in horizontal direction one-by-one. As a cleaning method using the substrate cleaning apparatus, a spray method, a brush method, a combination of the methods or the like are known. In the spray method, purified water or chemicals are sprayed on a substrate. In the brush method, a roll brush mechanically removes foreign objects. In the substrate cleaning apparatus, when a rear face of a glass substrate is cleaned, the substrate receives an upward pressure from the rear face. Therefore, the glass substrate is conveyed, while suppressing the upward pressure to the glass substrate (as for an example of a substrate cleaning apparatus of the above-mentioned brush method, for example, refer to Japanese Patent Application Laid-Open No. 1993-198544 (2-4 pages and FIG. 1)).
Since removing foreign objects mechanically by the roll brush, the brush method works excellently. However, even the method may be insufficient in cleaning the rear face of the substrate. The difficulties are described with reference to FIGS. 9, 10A and 10B. FIG. 9 is a side view which illustrates a configuration of a typical brush cleaning unit. FIG. 10A shows a typical roll brush. FIG. 10B shows that a roll brush is cleaning the rear face of the glass substrate.
As shown in FIG. 9, the brush cleaning unit 1 includes a brush cleaning mechanical section, a spray cleaning mechanical section and a transporting mechanical section. The brush cleaning mechanical section includes a roll brush 10 which touches the rear face of the glass substrate 3 while rotating, and a roll brush moving section 7 which moves the roll brush 10 up and down. The spray cleaning mechanical section includes an upper spray 6a which sprays purified water or chemicals from jet orifices arranged over the glass substrate 3 to clean a front face thereof. The spray cleaning mechanical section further includes a lower spray 6b which sprays purified water or chemicals from jet orifices arranged below the glass substrate 3 to clean the rear face thereof. The transporting mechanical section includes a conveyance roller 4 which moves the glass substrate 3 in a direction perpendicular to longitudinal of the roll brush 10, and a rising preventing roller 5 which prevents the glass substrate 3 from rising.